Answer: A) They must have the same slope.
Step-by-step explanation:
The slope of the Total revenue curve is the marginal revenue and likewise the slope of the Total cost curve is the marginal cost. The profit maximising level of output is the output level where Marginal revenue is equal to Marginal cost.
As the Marginal cost and the Marginal revenue are equal at this point, the slopes of the total revenue and the total cost must be the same as well.